Lemma 2.7 [1]}
Let \(N\)  be a natural number, \(A\)  a spectral set in \(\mathbb {Z}_{N}\)  and \(p\)  a prime divisor of \(N\) . Assume that \(S-T(\mathbb {Z}_{\frac{N}{p}})\) . If \(A\)  is the union of \(\mathbb {Z}_{p}\) -cosets, then \(A\)  tiles \(\mathbb {Z}_{N}\) .

